The general goals of the proposed program are to achieve an understanding of some aspects of the synthesis, structure and function of certain important RNA components of prokaryotes and eukaryotes. The immediate focus of the program is upon the following specific points: 1) The continuation of the purification and characterization of the RNase M5 of B. subtilis. 2) The continuation of the analysis of the RNase M5-p5A rRNA recognition process: study of a model protein-polyribonucleotide interaction. 3) The search for novel rRNA processing endonucleases in prokaryotes. 4) The analysis of the function of precursor-specific segments of p5A rRNA. 5) The continuation of the isolation and analysis of a substrate-specific "scavenging" nuclease from B. subtilis. 6) The continuation of the detailed study of structural and functional aspects of mouse 5.8S rRNA. 7) The study of selected nucleotide sequences in the mouse nucleolar 32S rRNA precursor: derivation of a detailed restriction endonuclease map of mouse rDNA. 8) The analysis of ribosomal protein binding sites in 5.8S rRNA and in the 5.8S rRNA oriented in complex with 28S rRNA. 9) The search for rRNA-processing enzymes of mouse cells.